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High-Payoff Space Transportation Design Approach with aTechnology Integration StrategyC. M. McCleskeyl and R. E. Rhodes and2NASA Kennedy Space Center, Florida, 32899T. Chen3NASA Marshall Space Flight Center, Huntsville, Alabama, 35812andJ. Robinson4The Boeing Company, Huntington Beach, California, 92647A general architectural design sequence is described to create a highly efficient, operable,and supportable design that achieves an affordable, repeatable, and sustainabletransportation function. The paper covers the following aspects of this approach in moredetail: (1) vehicle architectural concept considerations (including important strategies forgreater reusability); (2) vehicle element propulsion system packaging considerations; (3)vehicle element functional definition; (4) external ground servicing and accessconsiderations; and, (5) simplified guidance, navigation, flight control and avionicscommunications considerations. Additionally, a technology integration strategy is forwardedthat includes: (a) ground and flight test prior to production commitments; (b) parallel stagepropellant storage, such as concentric-nested tanks; (c) high thrust, LOX-rich, LOX-cooledfirst stage earth-to-orbit main engine; (d) non-toxic, day-of-launch-loaded propellants forupper stages and in-space propulsion; (e) electric propulsion and aero stage control.Aerospace Technologist, Engineering Directorate, Kennedy Space CenterINE-D2, and AIAA Senior Member.Aerospace Technologist, Engineering Directorate, Kennedy Space CenterlNE-D2, and AIAA Senior Member.3 Insert Job Title, Department Name, AddresslMail Stop, and AIAA Member Grade for third author.4 Insert Job Title, Department Name, AddresslMail Stop, and AIAA Member Grade for fourth author (etc).121American Institute of Aeronautics and Astronautics092407
High-Payoff Space Transportation Design Approach with aTechnology Integration StrategyC. M. McCleskeyl and R. E. Rhodes2NASA Kennedy Space Center, Florida, 32899T.T. Chen 3NASA Marshall Space Flight Center, Huntsville, Alabama, 35812l.W. Robinson4The Boeing Company (ret), Huntington Beach, Califorma, 92647This paper describes a general approach for creating architectural concepts that arehighly efficient, operable, and supportable, in turn achieving affordable, repeatable, andsustainable space transportation. The paper focuses on the following: (1) vehiclearchitectural concept considerations (including important strategies for greater reusability);(2) vehicle element propulsion system packaging considerations, including integrated mainand auxiliary propulsion systems; (3) vehicle element functional integration; (4) groundelement functional integration; (5) simplified and automated electrical power and avionicsintegration; and, (6) ground and flight test prior to production commitments. Additionally,we have provided four essential technologies enabling the high payoff design approach: (a)parallel stage propellant storage, such as concentric-nested tanks, for more efficient spacevehicle design and operation; (b) high thrust, L02-rich, L02-cooled first stage earth-to-orbitmain engine; (c) non-toxic, day-of-Iaunch-Ioaded propellants for upper stages and in-spacepropulsion; and (d) electric propulsion and flight controls.NomenclatureASTFCH4EHAEMAETOGRCGSEHMFI spKSCLIDLH2L02LRU Aft Skirt Test Facility Methane Electro-Hydrostatic Actuator Electro-Mechanical Actuators Earth-to-Orbit Glenn Research Center Ground Support Equipment Hypergolic Maintenance Facility Speclfic Impulse Kennedy Space Center Length-to-Diameter ratio LiqUld Hydrogen Liquid Oxygen Line Replacement UnitMPSMRO&MOMLRP-lSCAPESPSTSRBSSMETPMTPSTVC Main Propulsion System Mixture Ratio Operations and Maintenance Outer Mold Line Rocket Propellant - I Self-Contained Atmospheric ProtectiveEnsemble Space Propulsion Synergy Team Solid Rocket Booster Space Shuttle Main Engine Technical Performance Measures Thermal Protection System Thrust Vector Control1 Aerospace Technologist, Engineering Directorate, NASA Kennedy Space Center, mail code NE-Dl, and AIAASenior Member.2 Aerospace Technologist, Engineering Directorate, NASA Kennedy Space Center, mail code NE-Dl, and AIAASenior Member.3 Lead Aerospace Engineer, Spacecraft and Vehicle Systems Department, NASA Marshall Space Flight Center, mailcode EV-91, and AIAA Senior Member.4 The Boeing Company (retired); chairman, Space Propulsion Synergy Team, and AIAA Associate Fellow.1American Institute of Aeronautics and Astronautics071311
IntroductionA six-step sequential process is suggested to provide a general architectmal design sequence to create a highlyefficient, operable, and supportable design that achieves an affordable and economically sustainable transportationfunction. The six critical, sequential steps are·Six Critical Steps to an Affordable, Economically Sustainable System DesignI. Simplify the vehicle/ground system architecture2. Efficiently package each vehicle element's propulsion system (i.e., tank, engine and compartment layouts)3. Integrate vehicle element functions into the lowest number of subsystems/components with mmimum groundsupport requirements4. Integrate ground elementfunctions into the lowest number ofwork stations, facilities, and support equipment5. Simplify avionics andflight control design into minimum components, then, power and automate what's left6. Extensively flight test to demonstrate accomplishment of all production and operations needs and objectives forfull operational system capability with the affordability objective metThese steps are important to perform during early conceptual design to avoid the accumulation of unaffordabledesign, development, production, and ground operations work. Through adherence to these steps, one can also avoidtime delays that cause added expenditures, as well, and thus achieve the objectives of life cycle affordability andoperational sustainability.Each of the steps discuss the specifics of the approach followed by a section identifying how each stepaddresses technical criteria that influence space transportation affordability and sustainability. This paper uses thelist of criteria developed by the Space Propulsion Synergy Team (SPST), a NASA-sponsored volunteer group ofexperienced government, industry and academia colleagues in the space propulsion community. 1Specifically, the SPST identified eighteen (18) highly influential criteria as design drivers of spacetransportation affordability and sustainability. Selected from among 64 candidate design drivers, these eighteenmeasurable criteria were previously determined by the SPST to be the most important to understand and controlduring the design cycle for achieving life cycle affordability. An in-depth treatment of these criteria and theirinfluence on life cycle affordability and sustainability are provided in the referenced Joint Propulsion Conferencepaper. 2This paper adds another criterion to these eighteen-reusability. For the purposes of this paper, reusability is theability of a system, or parts of a system, to be reused for multiple flights.A system with low reusability requires a high degree of work for its next flight. A system with high reusabilityis assumed to be one that fully retains its functional integrity between flights, and thus little or no work is requiredother than payload handling and propellant servicing. Highly reusable systems are more affordable by (1)minimizing routine purchases of high-value flight equipment by its owner-operator, (2) reducing routinemaintenance expense, and (3) increasing system productivity through shorter processing durations. Therefore, wecan logically conclude that highly reusable system design techniques and advanced technologies are needed toenable affordable and sustainable space transportation.The affordability benefits due to reusability become less clear when comparing low reusability systems (e.g.,ocean-retrieved elements) with fully expendable systems.The total list of nineteen (19) criteria (i.e., the 18 derived by the SPST plus the reusability criterion explainedabove), and their correlation with key life cycle affordability parameters derived by the authors, is shown in Table 1.The paper concludes by identifying specific technologies and design approaches that support the steps described inachieving the overall objectives of affordability and economic sustainability.2American Institute of Aeronautics and Astronautics071311
Step 1.Simplify the Vehicle ArchitectureA. Discussion/SpecificsSimplify the vehicle by minlmizmg the number ofunique vehicle elements and maximize reusability m those thatremain in the concept.This keeps the number of production and operations ground stations to a minimum, and therefore, holds themarginal and fixed operating costs to a minimum. A high degree of reusability allows the owner-operator tominimize the requirement for routinely purchasing high-value flight equipment and replacement parts. Theminimum number of elements minimizes unique annual fixed costs associated with the production, supply,servicing, and maintenance of each unique stage or element. Finally, a simplified flight system made up of aminimum number of elements enables a simplified ground system. A simplified ground system not only reducesfixed infrastructure support costs, but also decreases direct operating costs per flight and greater flight throughput byreducing work content and eliminating time-consuming work. As a result of the reduced work and time, the systemutilization, affordability, and sustainability for the equipment owner-operator are all improved.B. Specific Engineering Criteria Addressed for ImprovementStep I directly addresses about half of the nineteen (19) engineering criteria for achieving affordable andsustainable space transportation systems (reference Error! Reference source not found. for specific correlations toaffordability); Percentage ofelements and systems that are highly reusable Total number ofseparate identified vehicle propulsion systems and/or separate stages Total number offlight tanks m the architecture Number ofmaintenance actIOns unplanned before or between missions Number ofmamtenance actions planned before or between missions Total number oftraditional ground interfqcefunctions required Total number ofvehicle element-to-element support systems Number offlight vehicle servicmg mterfaces Number ofconfined/closed compartments Number ofmechanical element matmg operationsStep 2.Efficiently Package Each Vehicle Element's Propulsion SystemA. Discussion/SpecificsAchieve a far more compact vehicle design whose cryogenic propulsion systems are far simpler to operate inflight and on the ground than current design approachesThe design strategy contains a number of specifics for achieving this, and is enabled through:1. Use of minimum number of main and auxiliary propellant commodities. preferably confined to dav-oflaunch-loaded oxygen and hydrogen only. The idea is to keep the accumulation of design effort, recurringproduction work, and ground processing time and expense to a minimum. Separate propulsion systems areadditive to theses life cycle cost elements.2. Keep ground interface connections close to ground level to avoid a series of elevated. articulatmgumbilrcals-particularly. lrfi-offumbilicals O.e. those that remain connected until vehicle first-motion or.T-O umbilicals). Avoiding large structures keeps ground system development and maintenance costs down.When such systems are outfitted with active mechanical, plumbing and electrical systems, the development,maintenance and operations costs go up. Also, the responsiveness of the system to produce a launch goes up.3. Avoid production complexities. operational propellant loading complexities. and safety risks ofspecifymgcommon-bulkhead tandem tank arrangements and separate auxiliary propulsion systems.4. Use concentric-nested propellant tanks arranged such that complex feed systems and other externalsubsystems are eliminated (note concentric-nested means one tank is concentrically arranged insideanother. but no common wal/). This approach eliminates long feed lines and a number of active supportsubsystems for the propulsion function; e.g., long propellant feed lines for the pump feed system, L02"pogo" suppression system, anti-geysering and thermal conditioning sub-systems. Furthermore, concentricnested tank concepts minimize the volume and weight of the total system. As such, the approach has wideand far-reaching architectural implications across a number of space transportation applications and acrossthe space transportation life cycle. It also allows the incorporation of advanced concepts such as integrating3American Institute of Aeronautics and Astronautics071311
the turbo-pump into the main propellant tank sump, further avoiding the need for added sub-systemspreviously mentioned.5 Use a minimum number of main engines with a minimum amount ofturbo-machinery and interconnectingmain propulsion system plumbmg. The more main engines (meaning devices incorporating feed turbomachinery, combustion chambers, and exhaust nozzles) there are in the system, the more interconnectingplumbing, avionics, software and opportunities for reliability problems accumulate. This rapidly expands theeffort required to: design the main propulsion system, develop and test, continually manufacture(particularly if expended each flight), process on the ground, and control risk in flight.6. Use electric propellant valve actuation and eliminate distributed hydrauhc and pneumatic prrmary and backup systems from all engine and propellant system controls (including thrust vector control. but only ifdifferential required). This approach avoids numerous support systems for the propellant valve controlsand/or gimbaled engines and reduces the number of support systems for the flight vehicle and groundsupport equipment. It also means fewer parts to produce and less assembly work leading to more flights inshorter times with less effort.7. In the longer-term. consider usmg L02-rich. L02-cooled mam engine combustion for first stage earth-toorbit propulsion that adjusts the mixture ratio back toward stoichiometric ratio as the thrust requirement isreduced durmg ascent. This concept reduces the combined propellant tank volume, and hence reducesvehicle length and dry weight. This allows a more efficient design for both flight and ground operations. Italso better enables the design criteria of minimum number of propellants since it avoids having to useunique, high thrust propellant combinations applicable to lower-altitude, fIrst stage flight only. Use of solidboosters or kerosene is generally seen as benefIcial for low-altitude, fIrst stage flight where specifIc impulseis traded for higher thrust. This concept uses a common set of propellants throughout the ascent phase andvaries the thrust/Isp characteristics during flight with a minimum number of dedicated systems.B. Specific Engineering Criteria Addressed for ImprovementStep 2 enables or directly addresses at least twelve (12) of the nineteen (19) engineering criteria for achievingaffordable and sustainable space transportation systems (reference Table 1 for specifIc correlations to affordability); Total number ofseparate identified vehicle propulsion systems and/or separate stagesPercentage ofelements and systems that are highly reusableTotal number oftraditIOnal ground mterfacefunctions requiredNumber offlight vehicle servicing interfacesNumber ofdifferent fluids requiredNumber ofsafety driven functional requirements to mamtam safe control ofsystems durrngfllght and groundoperationsNumber ofconfined/closed compartmentsNumber ofsafety driven limited access control operationsNumber ofmaintenance actIOns unplanned before or between miSSIOnsNumber ofmaintenance actions planned before or between missionsNumber ofcommodities used that require medical support operations and routme trainingNumber ofCriticality 1 system andfailure analysis modesStep 3.Integrate Vehicle Element Functions into the Lowest Number of Subsystems/ComponentsA. Discussion/SpecificsCreate a generrc functional systems breakdown structure for each conceived vehicle element. and combine (ormtegrate) as many functions mto smgular systems to provide a minimum ofstandalone. dedicated subsystems. 3 Thiswill minimize the number of accumulated subsystems and supporting components for a given set of requiredfunctions. For example, combme various propulsion and power functions with common propellants and fluidcommodities to avoid separate fIll and drain, storage and distribution subsystems, ground interfaces, and GSE. Also,use technical approaches that inherently require fewer separate support subsystems to perform the function (e.g., useelectric actuation to displace distributed hydraulics and its. support subsystems and GSE). In so doing, thecumulative design and development effort for both flight and ground support systems is greatly reduced. Therecurring production effort is likewise reduced, along with the attendant number of separate suppliers requit:ed to4American Institute of Aeronautics and Astronautics071311
sustain the system. The recurring ground operations work and processing time are reduced, as well as recurringlabor, materials, and other direct costs.B. Specific Engineering Criteria Addressed for ImprovementStep 3 enables or directly addresses a large number of the nineteen (19) engineering criteria for achievingaffordable and sustainable space transportation systems (reference Table 1 for specific correlations to affordability); Total number offlight tanks in the architecture Total number ofseparate identified vehicle propulsion systems and/or separate stages Total number oftraditional ground interface functIOns required Number offlight vehicle servicing interfaces Number ofdifferent fluids required Number ofsafety driven functional requirements to mamtam safe control ofsystems during flight and groundoperations Number ofconfined/closed compartments Number ofsafety driven limited access control operations Number ofmamtenance actIOns unplanned before or between missIOns Number ofmaintenance actions planned before or between missions Number ofcommodities used that require medical support operations and routine training Number ofCriticality I system andfailure analysis modes Number ofsafing operations at landing (for reusable elements)Step 4.Integrate ground element functions into the lowest number of work stations, facilities, andsupport equipmentA. Discussion/SpecificsKeep routine external ground servicing and access reqUirements simple and to a minimum: e.g., strive for nomasts or towers:The design strategy contains a number of specifics for achieving this, and is enabled through:1. Avoid breakmg the functIOnal mtegritv of any flight systems during ground turnaround operatIOns. Forhighly reusable system designs, the objective is to avoid electrical and plumbing disconnections, along withmechanical system disconnections that would require re-rigging, re-calibration, re-alignment, andfunctional checkout. Minimize any operator "closeout" activity by design. This will significantly reduceroutine ground operations work and time required to produce a flight.2. Require the flight systems to be designed for mamtamabilitv as a means for achieving reliabilitv and sa(etvobjectives. This avoids the need to go into a maintenance station during ground turnaround operations.3. Locate internal line replacement units (LRUs) near outer mold-line to avOid all mternal access forinstallation and/or routme change-out. Doing so eliminates the need for internal access kits for routineoperations, conditioned air, controlled personnel entry and drag-on lighting.4. Strive to remove as many closed vehicle compartments as possible. This approach minimizes subsystemhardware and routine ground operations required in such compartments, i.e. purges and hazardous gasdetection su
Ensemble Space Propulsion Synergy Team Solid Rocket Booster Space Shuttle Main Engine Technical Performance Measures Thermal Protection System Thrust Vector Control 1 Aerospace Te
